Crusta tenuis est.

Crusta is nominative singular feminine.

Why:

• The sentence has est = is
• In a basic X is Y sentence, the subject is normally in the nominative
• Crusta is a first-declension noun

So here crusta is the subject of the sentence.

Because tenuis is a third-declension adjective, not a first/second-declension one.

Its nominative singular forms are:

• masculine: tenuis
• feminine: tenuis
• neuter: tenue

Since crusta is feminine singular nominative, the adjective must also be feminine singular nominative, and for this adjective that form is tenuis.

So:

• crusta bona would use a first/second-declension adjective
• but crusta tenuis uses a third-declension adjective

Yes. Adjectives in Latin agree with the nouns they describe in:

• gender
• number
• case

Here:

• crusta = feminine, singular, nominative
• tenuis = feminine, singular, nominative

Even though the endings are different from what an English speaker might expect, they still match grammatically.

Latin word order is much freer than English word order.

In English, you usually need:

• subject + verb + complement

But in Latin, Crusta tenuis est is normal, and so are other arrangements such as:

• Crusta est tenuis
• Tenuis crusta est
• Tenuis est crusta

The ending position of est is very common in Latin prose. The endings on the words show their roles, so Latin does not depend on word order as heavily as English does.

Sometimes, yes, but it depends on context.

Latin can sometimes leave out est when the meaning is obvious, especially:

• in poetry
• in compressed style
• in sayings or labels

So Crusta tenuis could sometimes mean the crust is thin.

However, in normal straightforward prose for learners, Crusta tenuis est is the full and standard form.

Latin has no articles like English a, an, or the.

So crusta can mean:

• a crust
• the crust
• sometimes just crust

Which one is best in English depends on context, not on a separate Latin word.

That is very normal in Latin and is something English speakers often need time to get used to.

Here it is an adjective, yes.

A dictionary entry would usually look something like:

• tenuis, tenue

It can mean things such as:

• thin
• fine
• slender
• slight

The exact English word depends on context. In this sentence, it is simply describing crusta.

The form crusta is a strong clue. A noun ending in -a in the nominative singular is very often first declension.

Its basic pattern would be like this:

• nominative singular: crusta
• genitive singular: crustae

So if you saw it in a dictionary, you would expect something like crusta, crustae.

Because first-declension nouns are usually feminine, that also helps explain why the adjective is in a feminine form.

In Classical Latin, a reasonable pronunciation is:

• crusta: KROOS-tah
• tenuis: TEH-noo-iss or TEH-nu-iss
• est: est

A more careful classical breakdown is:

• crus-ta
• te-nu-is
• est

A few useful points:

• c is always hard, like k
• u is pronounced like oo
• tenuis has three syllables

Yes. Latin allows both:

• Crusta tenuis est
• Tenuis crusta est

Both are grammatical.

Sometimes word order can give slight emphasis or style, but the basic meaning stays the same. For a beginner, the important point is that the adjective does not have to stand before the noun the way it usually does in English.

It is a simple sentence with:

• a subject: crusta
• a linking verb: est
• a predicate adjective: tenuis

So the structure is:

noun + adjective + form of esse

This is a very common Latin pattern:

• Puella laeta est
• Via longa est
• Crusta tenuis est

In each case, the adjective describes the subject through the verb est.